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rule win_lurk_auto { meta: author = "Felix Bilstein - yara-signator at cocacoding dot com" date = "2022-05-16" version = "1" description = "Detects win.lurk." info = "autogenerated rule brought to you by yara-signator" tool = "yara-signator v0.6.0" signator_config = "callsandjumps;datarefs;binvalue" malpedia_reference = "https://malpedia.caad.fkie.fraunhofer.de/details/win.lurk" malpedia_rule_date = "20220513" malpedia_hash = "7f4b2229e6ae614d86d74917f6d5b41890e62a26" malpedia_version = "20220516" malpedia_license = "CC BY-SA 4.0" malpedia_sharing = "TLP:WHITE" /* DISCLAIMER * The strings used in this rule have been automatically selected from the * disassembly of memory dumps and unpacked files, using YARA-Signator. * The code and documentation is published here: * https://github.com/fxb-cocacoding/yara-signator * As Malpedia is used as data source, please note that for a given * number of families, only single samples are documented. * This likely impacts the degree of generalization these rules will offer. * Take the described generation method also into consideration when you * apply the rules in your use cases and assign them confidence levels. */ strings: $sequence_0 = { ff7508 ff15???????? 8b35???????? 50 ff7508 } // n = 5, score = 1100 // ff7508 | push dword ptr [ebp + 8] // ff15???????? | // 8b35???????? | // 50 | push eax // ff7508 | push dword ptr [ebp + 8] $sequence_1 = { 8b4508 5b 5f 5e c9 c3 55 } // n = 7, score = 900 // 8b4508 | mov eax, dword ptr [ebp + 8] // 5b | pop ebx // 5f | pop edi // 5e | pop esi // c9 | leave // c3 | ret // 55 | push ebp $sequence_2 = { 8b45fc eb3b e8???????? a1???????? } // n = 4, score = 800 // 8b45fc | mov eax, dword ptr [ebp - 4] // eb3b | jmp 0x3d // e8???????? | // a1???????? | $sequence_3 = { ff4508 8907 83c704 837d0808 72e3 } // n = 5, score = 800 // ff4508 | inc dword ptr [ebp + 8] // 8907 | mov dword ptr [edi], eax // 83c704 | add edi, 4 // 837d0808 | cmp dword ptr [ebp + 8], 8 // 72e3 | jb 0xffffffe5 $sequence_4 = { 6a40 8945e8 ffd7 6a50 } // n = 4, score = 800 // 6a40 | push 0x40 // 8945e8 | mov dword ptr [ebp - 0x18], eax // ffd7 | call edi // 6a50 | push 0x50 $sequence_5 = { eb09 8b45fc 83c001 8945fc 8b4dfc 3b0d???????? 0f8394000000 } // n = 7, score = 800 // eb09 | jmp 0xb // 8b45fc | mov eax, dword ptr [ebp - 4] // 83c001 | add eax, 1 // 8945fc | mov dword ptr [ebp - 4], eax // 8b4dfc | mov ecx, dword ptr [ebp - 4] // 3b0d???????? | // 0f8394000000 | jae 0x9a $sequence_6 = { 8b45d4 40 40 8945d4 e9???????? 8b45c0 8b4dc0 } // n = 7, score = 800 // 8b45d4 | mov eax, dword ptr [ebp - 0x2c] // 40 | inc eax // 40 | inc eax // 8945d4 | mov dword ptr [ebp - 0x2c], eax // e9???????? | // 8b45c0 | mov eax, dword ptr [ebp - 0x40] // 8b4dc0 | mov ecx, dword ptr [ebp - 0x40] $sequence_7 = { 8b45d8 8b4dd8 03483c 894dd0 8b45d0 83c078 8945ec } // n = 7, score = 800 // 8b45d8 | mov eax, dword ptr [ebp - 0x28] // 8b4dd8 | mov ecx, dword ptr [ebp - 0x28] // 03483c | add ecx, dword ptr [eax + 0x3c] // 894dd0 | mov dword ptr [ebp - 0x30], ecx // 8b45d0 | mov eax, dword ptr [ebp - 0x30] // 83c078 | add eax, 0x78 // 8945ec | mov dword ptr [ebp - 0x14], eax $sequence_8 = { eb09 8b45ec 83c001 8945ec 8b4dd4 0fb75106 3955ec } // n = 7, score = 800 // eb09 | jmp 0xb // 8b45ec | mov eax, dword ptr [ebp - 0x14] // 83c001 | add eax, 1 // 8945ec | mov dword ptr [ebp - 0x14], eax // 8b4dd4 | mov ecx, dword ptr [ebp - 0x2c] // 0fb75106 | movzx edx, word ptr [ecx + 6] // 3955ec | cmp dword ptr [ebp - 0x14], edx $sequence_9 = { 55 8bec 83ec0c 53 56 8b7508 0fb606 } // n = 7, score = 800 // 55 | push ebp // 8bec | mov ebp, esp // 83ec0c | sub esp, 0xc // 53 | push ebx // 56 | push esi // 8b7508 | mov esi, dword ptr [ebp + 8] // 0fb606 | movzx eax, byte ptr [esi] $sequence_10 = { ff37 e8???????? 83c418 85c0 ff37 6a00 7519 } // n = 7, score = 800 // ff37 | push dword ptr [edi] // e8???????? | // 83c418 | add esp, 0x18 // 85c0 | test eax, eax // ff37 | push dword ptr [edi] // 6a00 | push 0 // 7519 | jne 0x1b $sequence_11 = { 8b7e04 ff7508 037e08 ff15???????? } // n = 4, score = 800 // 8b7e04 | mov edi, dword ptr [esi + 4] // ff7508 | push dword ptr [ebp + 8] // 037e08 | add edi, dword ptr [esi + 8] // ff15???????? | $sequence_12 = { 6a1a 5f f7ff a1???????? 57 80c261 } // n = 6, score = 800 // 6a1a | push 0x1a // 5f | pop edi // f7ff | idiv edi // a1???????? | // 57 | push edi // 80c261 | add dl, 0x61 $sequence_13 = { 68???????? 8d85ecfeffff 50 ff15???????? 8d85ecfeffff 50 68???????? } // n = 7, score = 800 // 68???????? | // 8d85ecfeffff | lea eax, [ebp - 0x114] // 50 | push eax // ff15???????? | // 8d85ecfeffff | lea eax, [ebp - 0x114] // 50 | push eax // 68???????? | $sequence_14 = { 7519 6a01 8d460b 50 e8???????? 59 } // n = 6, score = 800 // 7519 | jne 0x1b // 6a01 | push 1 // 8d460b | lea eax, [esi + 0xb] // 50 | push eax // e8???????? | // 59 | pop ecx $sequence_15 = { 8b7df8 81e7ffff0000 56 ff15???????? } // n = 4, score = 800 // 8b7df8 | mov edi, dword ptr [ebp - 8] // 81e7ffff0000 | and edi, 0xffff // 56 | push esi // ff15???????? | condition: 7 of them and filesize < 5316608 }
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